Interested in Language
Could you help me to understand the difference between 'know' and 'know of'?
Do you know of any doctor?
Do you know any doctor?
Q. Who is that person you mentioned just now?
A. We've never met, but I certainly know of him.
The expression ‘not/none that I know of’ is standard spoken phrase to answer in the negative (I do not know). As an example, when you're asked "Is there a planet other than the earth that sustains life?
You can say: "None that I know of." (It means you think it may be possible that there is, but you don't know or heard about it.)